The invention pertains to the field of recreational vehicle power supply systems using rechargeable battery circuits.
Recreational vehicles, such as travel trailers, motor homes, and campers, and watercraft such as boats and houseboats, are often provided wth dual electrical systems. Lights, and many of the light duty appliances, such as water pumps, usually operate at 12 volts DC, while the heavy duty equipment, such as air conditioners, television sets, and some refrigerators, require 120 volt AC electrical power. While some of the larger vehicles employ generators and auxiliary engines for producing electricity, the majority of "self-contained" recreational vehicles and boats employ auxiliary rechargeable batteries and converters to energize the unit.
A recreational vehicle converter includes a transformer having a primary coil connectible to an AC power supply. The transformer secondary coil energizes a rectifying circuit such that the converter has an approximately 12 volt direct current output which is connected to the recreational vehicle load circuit. As the vehicle battery is also of 12 volts the lighting and low voltage circuit of the recreational vehicle may be selectively powered by the battery, or the converter output. With such recreational vehicle circuits it is common to utilize means for switching between battery and converter operation, and the circuitry usually employs a slow or trickle battery charging circuit supplied from the converter output for recharging the auxiliary vehicle battery during converter operation as powered from an alternating current power source.
It is not unusual for the vehicle auxiliary battery to become substantially discharged due to extended use while the vehicle is in the field and accessibility to alternating current is not possible. Accordingly, when the vehicle is at a location where alternating current is available it is often desired to quickly bring the auxiliary battery to a fully charged condition, and, with known techniques, a battery fast charge may be connected to the vehicle alternating current supply for bringing the auxiliary battery to a full charge in a relatively short time. However, the rapid charging of wet cell rechargeable batteries presents certain well known hazards and conditions, and the rate and duration of fast charging must be closely controlled in order to prevent damage to the battery or the formation of explosive gases.
Both cost and size are significant factors in the designing of recreational vehicle electrical circuits and to utilize a plurality of transformers and rectifiers to attain selective recreational vehicle load operation, as well as permit slow and fast charging, is prohibitive in many instances, and heretofore a recreational vehicle direct current power supply system capable of both slow and fast charging has not been available which is of a minimum cost and size, dependable and safe in operation and readily operable by the unskilled.